title: Changes in pulse pressure following fluid loading: a comparison between aortic root (non-invasive tonometry) and femoral artery (invasive recordings).
abstract: OBJECTIVE
  To document the relationship between stroke volume (SV) and pulse pressure (PP) recorded at the femoral and aortic sites during volume expansion (VE) in patients in shock. We hypothesized that non-invasively estimated aortic PP would exhibit the same ability as PP recorded invasively at the femoral level to track SV changes.
  
  
  METHODS
  Included in this prospective study were 56 ICU patients needing VE. Femoral PP (indwelling catheter), aortic PP (tonometry) and cardiac output (thermodilution) were recorded before and after VE. Responders were defined as patients who showed an increase in SV of ≥15% after VE.
  
  
  RESULTS
  Of the 56 included patients in shock, 39 (age 57 ± 14 years, SAPS II 46 ± 18) completed the study. At both sites, PP increased after VE in responders (n=17, mean SV increase 30 ± 15%) but not in non-responders. In the overall population, there was a positive relationship between VE-induced changes in SV and in PP at the femoral (r=0.60, p<0.001) and aortic (r=0.52, p<0.001) sites. Increases in femoral PP of ≥9% indicated SV increases of ≥15% with 82% sensitivity and 95% specificity. Increases in aortic PP of ≥4.5% indicated SV increases of ≥15% with 76% sensitivity and 82% specificity. Areas under the ROC curves indicated that aortic PP was not different from femoral PP for tracking changes in SV.
  
  
  CONCLUSIONS
  The ability of non-invasively estimated aortic PP to track fluid response was the same as that of invasively recorded femoral PP. This may have implications for non-invasive haemodynamic monitoring.
authors.affiliation: Service de Réanimation Médicale, Hôpital Bicêtre, Assistance Publique, Hôpitaux de Paris, Université Paris Sud 11, 78, rue du Général Leclerc, 94270 Le Kremlin-Bicêtre, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Dufour
authors.forename: Denis
authors.initials: D
authors.lastname: Chemla
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Teboul
authors.forename: Xavier
authors.initials: X
authors.lastname: Monnet
authors.forename: Christian
authors.initials: C
authors.lastname: Richard
authors.forename: David
authors.initials: D
authors.lastname: Osman
mesh_terms: D000328:Adult; D000368:Aged; D001011:Aorta / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D001795:Blood Pressure Determination / Q000295:instrumentation / Q000379:methods; D002302:Cardiac Output; D005263:Femoral Artery / Q000502:physiology*; D005440:Fluid Therapy; D006801:Humans; D007362:Intensive Care Units; D008365:Manometry; D008875:Middle Aged; D011446:Prospective Studies; D012769:Shock; D013318:Stroke Volume